Cardiac chemical constant. Part II: Application to normal and abnormal left ventricular function.
A physiochemical parameter has been defined as KD, the cardiac chemical equilibrium dissociation constant, and represents the ratio of long units (extended sarcomeres) to short units (contracted sarcomeres) of a hypothetical mid-wall circumferential fibre. KD has been separately identified for three specific points in the cardiac cycle: end-diastole (KDED), mid-cycle of systole (KDMC) and end-systole (KDES). These three values of KD have been computed for 15 normal patients (N), 6 patients with compensated volume overload (CVO), 9 patients with decompensated volume overload (DVO), 3 patients with compensated pressure overload (CPO) and 6 patients with congestive cardiomyopathy (CC). The average for the N group was KDED = 2.47, KDMC = 0.67 and KDES = 0.24. The majority of the long-to-short unit interconversions were calculated to occur during the first half of systole. The phenomenological model does not predict any significant parameter changes between the CVO group and the N group. The ratio KDMC/KDED is significantly reduced (P less than 0.05) for the DVO group compared to the N group and indicates a greater extent of long-to-short unit interconversion during the first half of systole for the DVO group average (compared to the N group average). For the CPO group, KDED averages around 45% higher than the average normal (P less than 0.005) and KDES averages about 33% lower than the average of the N group (P less than 0.005). As a compensatory process in CPO, the myocardium is transferring a larger percentage of its total units (sarcomeres) to long units at end-diastole and interconverting a larger percentage of its long units to short units during systole.(ABSTRACT TRUNCATED AT 250 WORDS)
Phillips
C A
CA
Department of Biomedical Engineering, Wright State University, Dayton, OH 45435.
D000328:Adult; D006328:Cardiac Catheterization; D002932:Cineangiography; D005260:Female; D006331:Heart Diseases / Q000000981:diagnostic imaging / Q000503:physiopathology*; D006349:Heart Valve Diseases / Q000503:physiopathology; D006439:Hemodynamics; D006801:Humans; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D009200:Myocardial Contraction / Q000502:physiology*; D009206:Myocardium / Q000378:metabolism; D013314:Stress, Mechanical